Manufacture of metal blanks



Patented May 12, 1925.

HUGO IlOHMAN'N, 0F BERLIN-JOHANNIS'II'HAL, GERMANY.

MANUFACTURE OF METAL BLANKS.

- No Drawing.

Application filed August 26, 1921. 'Serial No. 495,732.

(GRANTED UNDER THE 'rnovIsroNs or THE ACT or Manon 3, 1921, 41 sum. I.., 1313.

To all whom it may camera:

Be it known that I, HUGO LoHMANN,residing at 4 Sternp'latz, Berlin-Johannisthal, Germany, have invented certain new and useful Improvements in the Manufacture of Metal Blanks (for which I filed application in Germany Dec. 7, 1918), of which the following is a specification.

This invention relates to a process for the manufacture of tools, which are very hard,

" but ductile and capable of withstanding breakage, from metals, such as tuingsten,

titanium, molybdenum, chromium or iron.,

In addition to tools the metals obtainedcan also be used forother purposes. The hard properties of the materials hitherto employed for tools, are based on the amount of carbon they contain, the hardening having to be either effected by chilling or, in a second group, the amount of carbon which they contain is itself the cause of the hard ness, to the first group belong for example steel and the difierent steel alloys and to the second group belong silicon carbide and tungsten carbide. Both groups possess the disadvantage that the hard material is not ductile or very slightly so and therefore cannot be worked by forging, rolling, hammering and pressing operations. The manufacture of a material, which while retaining its hardness or even if the hardness be increased can be subjected toiworking processes, naturally means a great improvement.

The process is carried out by producing by a casting process a material which does not contain any phosphorus or with so little 'carbonin it that the properties of ductility are not impaired by rolling, forging and the like. This material exhibits the Well known crystalline structure and is therefore possessed of little power against breakage. It is now thoroughly worked by rolling, hammering, forging or pressing where by its crystalline structure is converted into a fibre-like or sinewy structure. The material is then subjected to a cementation process in a manner well known per se, carbon is added and a material or a tool is obtained with the above described properties.

As to-the casting process used in connection with my invention, I may say that the should be obtained by a suitable process,

for example the Bessemer process, and should have a carbon content of less than 0.3%, and it should be cast into bars of about 25 millimeters in diameter, which may be effected in chilled casings. Tungsten, chromium, titanium, and molybdenum required in the process are produced by'the reduction method by means of aluminium, in the form of bars of about 25 millimeters in diameter, or by any suitable process, but preferably by the process described in my United States Patents Nos. 1,224,242 and 1,212,426, by means of which a perfectly carbonless metal can be obtained. The bars of a diameter of about 25 millimeters produced in this manner are then rolled down, at a correspondingly high temperature, to a smaller diameter, the temperature employed being governed by the metallurgical properties of the metal to be treated; In treating molybdenum, titanium and tungsten, the temperature should range from about 1,200 to 1,400 degrees, centigrade. In dealing with chromium or iron, the temperature maybe reduced to 800 degrees C. Any variation of these temperatures does not" produce any change in the coarse crystalline structure of the particular metal. In a succeeding stage of the treatment the bars of substantially carbon free metal, produced as just described, and of which the diameter has been reduced to 12 millimeters and which exhibit a coarse crystalline structure, are cut up into blooms or strips of about 10 millimeters in length and are then submitted tomechanical treatment by rolling or hammering and are thus converted into tool blanks adapted to be machined to bring them to the desired shape, the desired fibrous structure upon which the mechanical strength of the tool depends bemg now imparted to the metal, In this treatment, however, in the case of tungsten, molybde-' num, and titanium, the temperature should not exceed 1,000 degrees (3., and, in the case of iron and chromium, it should not exceed 500 degrees 0., since only at temperature below these maximum temperatures can the fibrous structure-desired be obtained without danger of restoring the coarse crystalline texture by. recrystallization.

By a careful and systematic mechanical treatment, while closely observing the critical limits of temperature in order to avoid recrystallization, tools and the like having a very sinewy, fibrous texture are produced, which tools and the like have the qualities of being very resistant and firm against mechanical strains and stresses. The mechanical treatment referred to is at the same time instrumental in producing the required final shape which the tool is to possess when in use, for example as a tool for use in a rock drill or the like. The tool, which has mow acquired its final shape, is submitted to any of the Well-known carbonizing or cementation processes, for example to packing in a mixture of leather coal and barium oxide, care being taken to control the degree of heat in such a way as to prevent any change in the fibrous texture. These temperatures, in the case of tungsten, titanium and molybdenum, are at about 1,000 degrees centigrade, and,'in the case of chromium and iron, are at about 500 degrees centigrade. In the manner just described it is possible to manufacture tools which are, to the highest degree, resistant to all kinds of mechanical strains and stresses, such as blows, impact and the like, and which are not affected by oscillating vibrations and.

concussions, which are unavoidable during the operation of the tools. At the same time those portions of the tools which are submitted to the operating strains will'pos- 'sess the highest degree of hardness.

I claim: 1. Process for the manufacture of very hard, but ductile metal capable of withstanding breakage, consisting in casting ablock of carbonless crystalline metal, con verting its crystalline structure into a fibrelike structure, and then carbonizing said blocks. a v

2. Process for the manufacture of very hard, but ductile metal capable of withstanding breakage, consisting in casting a block of crystalline metal with so small a proportion of carbon that the metal remains ductile, converting its crystalline structure into a fibre-like structure, and then carbonizing said blocks." f

3. Process for the manufacture of very hard, but ductile metal capable of withstanding breakage, consisting in casting a block of carbonless crystalline metal, in converting its crystalline structure into a fibrelike structure, and in subsequent cementation of the metal.

hard, but ductile metal capable of with-' standing breakage, consisting in casting a block of carbonless crystalline metal such as tungsten, titanium, molybdenum, chromium or iron, converting its crystalline structure into a fibre-like structure, and then carbonizing said blocks.

6. Process for the manufacture of very hard, but ductile metal capable of withstanding breakage, consisting in casting a block of crystalline metal such as tungsten, titanium, molybdenum, chromium or iron, with so small a proportion of carbon that the metal remains ductile, converting its crystalline structure into a fibre-like structure, and then carbonizing said blocks.

7. Process for the manufacture of very hard, but ductile metal capable of with standing breakage, consisting in casting a block of carbonless crystalline metal, con verting its crystalline structure into a fibrelike structure, and then carbonizing said blocks by mechanical action.

. 8. Process for the manufacture of very hard, but ductile metal capable of withstanding breakage, consisting in casting a blockof crystalline metal with so small a proportion of carbon that the metal remains ductile, converting its crystalline structure into a fibre-like structure, and then carbonizing said blocks by mechanical action.

9. Process for the manufacture of very hard, but ductile metal capable of withstanding breakage, consisting in casting a block of carbonless crystalline metal, converting its crystalline structure into. a fibrelike structure, and then carbonizing said blocks by mechanical action such as rolling, hammering, forging or pressing.

10. Process for the manufacture of very hard, but ductile metal capable of withstanding breakage, consisting in casting a block of crystalline metal with so small a proportion of carbon that the metal remains ductile, converting its crystalline structure into a fibre-like structure by mechanical action such as roll1ng,hammer1ng, forging or .like structure by mechanical action, and in subsequent cementation of the metal.

12. Process for the manufacture of very hard, but ductile metal capable of with- In testimony whereof I have signed this standing breakage, consisting in casting a specification in the presence of two wit- 1 block of crystalline metal with so small a nesses. proportion of carbon that the metal remains 5 ductile, in converting its crystalline struc- HUGO LOHMANN' ture into a fibre-like structure by mechanical Witnesses: v actiop, and in subsequent cementation of the GUSTAV Ht'IBNER, meta Go'r'rnrna TUvIscH. 

